Automatically submerged sump pump



1948. w. L. WEEKS v AUTOMATICALLY SUBMERGED SUMP PUMP Filed Oct. 9, 1946INVENTOR WALTER L. WEEKS ATTORNEY Patented Dec. 7, 1948 AUTOMATICALLYSUBMERGED PUMP Walter L. Weeks, Wyckofl, N. J., aslignor to Corporation,a corpora- Wright Aeronautical tlon oi New York Application October 9,1948, Serial No. 702,248

11 Claims. 1

This invention relates to scavenge pumps and is particularly directed tothe provision of means for automatically maintaining a scavenge pumpsubmerged in the liquid to bescavenged.

Aircraft engines are generally provided with a so-called dry-sumplubrication system. In such a lubrication system, oil is stored in areservoir from which it is pumped to the various engine bearing surfacesby an engine driven pump. The oil drains from these bearing surfacesinto a sump from which it is returned to the reservoir by an enginedriven scavenge pump. In order to insure removal of substantially allthe oil from the engine sump under all engine operating conditions, thescavenge pump is provided with a capacity more than suflicient forreturning all the oil from the sump to the reservoir under the mostadverse pump operating conditions. This excess capacity of the scavengepump is essential in order to prevent oil fromoverflowing the sump.-Because of this excess capacity, during normal operation, the scavengepump returns a substantial amount of air or other gases with the oilback to the reservoir. The air and other gases become entrained withinthe oil and are only partially separated therefrom in the reservoir.This mixture of oil and gases is delivered from the reservoir to theengine lubricating oil pump thereby reducing the quantity of oildelivered to the various engine bearing surfaces by the last-mentionedpump. i

An object of this invention is to provide means for maintaining thescavenge pump submerged in spite of its excess capacity. To this end, arelief valve is provided which by passes oil back from the scavenge bumpinto the sump for recirculation through the scavenge pujnp whenever theoil level within the sump falls below a predetermined value. With thisarrangement, little or no gases are returned to reservoir by thescavenge pump.

Other objects of the invention will become apparent upon reading theannexed detailed description in connection with the drawing in which:Figure 1 is a, diagrammatic view of an engine dry-sump lubricationsystem;

Figure 2 is a sectional view of a Figure 1 embodying the invention;

Figure 3 is a sectional view oi of the invention.

Referring first to Figure l, a conventional radial cylinder engine,schematically indicated at I,

o l s p y portion of and a modified form is provided with a sump i! intowhich the oil drains from the variousengine bearing surfaces. From thesump II, the oil is returned to an 2 oil supply reservoir I4 throughpassage by means of an engine driven scavenge pump 22. A second enginedriven pump 24 draws oil from the reservoir l4 and supplies the oilunder pressure to the various bearing surfaces oi the engine throughpassages such as 28. The system so far described is quite conventional.

Referring now to Figure 2, the scavenge pump 22 isplaced in the bottomof the sump i! into which engine lubricating oil drains from the various engine bearing surfaces. The oil drains down to the inlet side 28 ofthe scavenge pump 2! .through an opening Ill and an oil filter 32. Theoutlet side 34 of the scavenge pump communicates with the passage IIthrough whichoil is returned by the scavenge pump to the supply 34 toits inlet side 28 of the scavenge pump 22,

The by-pass valve 36 is controlled by an engine driven pump 40, theoutput pressure of which urges the by-pass valve 38 to its closedposition. The control pump 40 is also disposed in the sump I2 and theinlet side of the control pump 40 communicates with the sump through apassage .42. Thecontrol pump 40 draws oil from the sump I! through thepassage 42 and pumps the oil back into the sump through a passagecontrolled by a pressure relief valve 46. The valve 46 is urged to itsclosed position against the output pressure of the pump 40 by a spring48 thereby determining the output pressure of the control pump 40. Theoutput pressure of the pump 40 acts against the upper end 50 of theby-pass valve 38 to urge the valve 38 to its closed position.

The construction is such that, when the level of the oil in the sump I2is above the inlet of the passage 42, the output pressure of the controlpump 40 acting against the end 50 of the valve I8 is sufficient to holdthe valve 8! closed against the output pressure of the scavenge pump 22.Under these conditions, the scavenge pump 22 returns oil to thereservoir I 4 in the normal manner and, because of the excess capacityof the scavenge Dummthe level of oil in the sump It, falls. when thelevel or the oil within the sump falls below the inlet to the passagel2, the output pressure of the pump It falls on whereupon the outputpressure of the scavenge pump 22 is sufllcient to raise and open thebypass valve 38. As a result, a substantial quantity of oil is returneddirectly to the sump by the scavenge pump 22 through the by-pass passage36, thereby reducing the net rate at which the scavenge pump returns oilfrom the sump to the oil supply reservoir H. The arrangement is suchthat the valve 38 opens to an extent that the pump 40 remains partiallyprimed. Thus, any increase in quantity of oil in the sump I2 results inan increase in the output pressure of the control pump 40 therebyeffecting a closing adjustment of the by-pass valve 28 whereupon therate at which the scavenge pump 22 removes oil from the sump to thesupply reservoir II is increased. Similarly, a decrease in the level ofthe oil in the sump below the inlet to the passage 42 results in adecrease in the output pressure of the control pump 40, therebyeflecting an opening movement of the valve 38 and decreasing the rate atwhich the scavenge pump removes oil from the sump to the supplyreservoirll.

With this construction, the level of oil in the sump remainssubstantially at the inlet to the passage 42 and, since this level isabove the top of the scavenge pump 22 and its inlet to the sump 12, thescavenge pump remains submerged in oil in spite of its excess capacity.Accordingly, only the gases mixed with the oil at the inlet of thescavenge pump are returned to the reservoir II by the scavenge pump.

Slots 52 are provided in the seat for the valve 48 to permit the escapeof gases therethrough.

In the absence of passages permitting the escape of gases delivered bythe control pump 80, when the level of the oil within the sump fallsbelow the inlet to the passage 42, the control pump may provide asuiiicient output gas pressure to hold the by-pass valve 28 closed.

As illustrated, the pump 48 preferably discharges oil into the sump I2through a stand pipe 54 which extends above the normal level of oilwithin the sump. In this way, gases delivered by the pump 40 are notmixed with the oil in the sump i2. Also, the capacity of the controlpump 40 preferably is considerably less than the capacity of thescavenge pump 22.

At low temperatures, the resistance offered by the passage to oil flowtherethrough is greater than at higher oil temperatures and, therefore,the discharge pressure of the scavenge pump 22 is higher at low oiltemperatures. In order to balance the increase valve opening pressure onthe by-pass valve 38 at low oil temperatures, the pressure relief valve46 may be designed to provide a higher control pump output pressure atlow oil temperatures. For example, a thermostat may beprovlded to helpurge the valve 48 toward its closed position at low oil temperatures, orthe discharge openings 55 may be made sufficiently small so that theincreased resistance to oil fiow thereth-rough at low temperaturesresults in' an increase in the output pressure of the con trol pump 40corresponding to the increase in the output pressure of the scavengepump 22.

Figure 3 illustrates a modified arrangement of the relief and by-passvalves together with a check valve in the return passage of the scavengeoil to the oil supply reservoir. In Figure "3, a scavenge pump ill and acontrol pump 82 are disposed within the engine sump with the inlet to 4the control pump disposed above the scavenge pump and its inlet as inFigure 2.

The scavenge pump 68 discharges oil into an outlet passage 84 and thencepast a check valve 68 to a passage 88 communicating with the oil supplyreservoir. The check valve 68 prevents return of oil from the reservoirback into the engine sump through the scavenge pump while the engine isshut down. The scavenge pump 68 can return oil directly to the sumpthrough a bypass passage 18 when a valve I2 is open. As in Figure 1, theby-pass valve 12 is urged to its closed position by the output pressureof the control pump 82 and a spring urged pressure relief valve 14 isprovided for controlling the output pressure of the control pump 62. Theoutput oil pressure of the control pump 62 opens relief valve ll againstits spring 18 and the control pump returns the oil to the sump throughopening 18 in the body of the valve 12 and through the passage 10. Also,the seat for the relief valve 14 has small openings 88 for the escape ofgases therethrough as in the modification of Figure 2.

As illustrated, the relief valve 14 and its spring 16 are disposedwithin the body of the by-pass valve 12 and, in addition, the stem 19has a sliding fit within the body of the by-pass valve, therebyproviding a compact valve arrangement. The operation of the by-passcontrol valves 12 and I4 is essentially the same as the operation of thecorresponding by-pass and control valves 38 and 48 of Figure 2.

With both aforedescribed modifications, the scavenge pump remainssubmerged in oil in spite of its excess capacity so that little or nogases are returned to the oil reservoir by the scavenge pump. Althoughthe invention has been described in connection with the dry-sumplubrication system of an engine, it should be apparent that theinvention is of general application. Thus, the invention may be usedwherever it is desired to keep a scavenge pump submerged in the liquidto be scavenged thereby.

While I have described my invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding my invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Iaim in the appended claims to cover all such modifications.

I claim as my invention:

1. In combination, a sump into which a liquid is arranged to drain, apump operable to remove liquid from said sump, a passage establishingcommunication between the outlet and inlet sides of said pump, a valvearranged to control said passage, said valve being urged in an opening.direction by the output pressure of said pump,

and means operable to hold said valve closed against said pump pressureonly when the level of the liquid is above said pump to a predeterminedextent.

2. In combination, a sump into which a liquid is arranged to drain, afirst pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passage establishingcommunication. between the outlet and inlet sides of said pump, a valvearranged to control said passage, and a second pump having its inletcommunicating with said sump at a level above' 'said first pump, theoutput pressure of said second pump being eflective to urge said' valveto its closed position.

3. In combination, a sump into which a liquid is arranged to drain, a'first pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passage establishingcommunication between the outlet and inlet sides of said pump, a valvearranged to control said passage, a second pump having itsinletcommunicating with said sump at a level above said first pump, theoutput pressure of said second pump being eifective to urge said valveto its closed position, and a pressure relief valve through which saidsecond pump returns liquid to said sump.

4. In combination, a sump into which a liquid is arranged to drain, afirst pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passage establishingcommunication between the outlet and inlet sides of said pump, a valvearranged to control said passage, a second pump having its inletcommunicating with said sump at a level above said first pump, theoutput pressure of said second pump being effective to urge said valveto its closed position, and a pressure relief valve through which saidsecond pump returns liquid to said sump, said pressure relief valvebeing movable with and relative to said first-mentioned valve.

5. In combination, a sump into which a liquid is arranged to drain, afirst pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passage establishingcommunication between the outlet and inlet sides oi said pump, a valvearranged to control said passage, as second pmnp having its inletcommunicating with said sump at a level above said first pump, theoutput pressure of said second pump being effective to urge said valveto its closed position, and a pressure relief valve through which saidsecond pump returns liquid to said sump, said pressure relief valvecooperating with a seat formed on said first-mentioned valve.

6. In combination, a sump into which a liquid is arranged to drain, afirst pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passage establishingcommimication between the discharge side of said pump and said sump, avalve arranged to control said passage, said valve being urged in anopening direction by the output pressure ofsaid pump, a second pumphaving its inlet commimicating with said sump at a level above saidfirst pump, the output pressure said second pump being effective to urgesaid valve toward its closed position.

7. An engine lubrication system comprising an oil supply reservoir, asump into which oil is arranged to drain from the engine bearingsurfaces, an engine driven scavenge pump operable for removing all fromsaid sump to said reservoir, means providing a passage which when, openestablishes communication between the discharge side of said pump andsaid sump, a valve arranged tocontrol said passage, and means for urgingsaid valve to its passage closing position when the oil level in saidsmnp exceeds a predetermined value.

I. An engine lubrication system comprising an oil supply reservoir, asump into which oil is arranged to drain from the engine bearingsurfaces, an engine driven scavenge pump having an inlet passagecommunicating with said sump and operable to remove oil from said sumpto said reservoir, a second passage which, when open, establishescommunication between the discharge side of said pump and said sump, avalve arranged to control said passage, and a second pump having itsinlet communicating with said sump at a level above said first scavengepump, the output pressure of said second pump being eifective to urgesaid valve toward its closed position.

9. An engine lubrication system comprising an oil supply reservoir, asump into which oil is arranged to drain from the engine bearingsurfaces, an engine driven scavenge pump having an inlet passagecommunicating with said sump and operable to remove oil from said sumpto said reservoir, a second passage which, when open, establishescommunication between the discharge side of said pump and said sump, avalve arranged to control said passage, a second pump having its inletcommunicating with said sump at a level above said first scavenge pump,the output pressure oi said second pump being eifective to urge saidvalve toward its closed position, and a pressure relief valve throughwhich said second pump returns liquid to said sump.

10. An engine lubrication system comprising an oil supply reservoir, asump into which oil is arranged to drain from the engine bearingsurfaces, an engine driven scavenge pump having an inlet passagecommunicating with said sump and operable to remove oil from said sumpto said reservoir, a second passage which, when open, establishescommunication between the discharge side of said pump and said sump, avalve arranged to control said passage, a second pump having its g inletcommunicating with said sump at a level above said first scavenge pump,the output pressure of said second pump being effective to urge saidvalve toward its closed position against the 7 output pressure of saidscavenge pump.

11. In combination, a sump into which a liquid is arranged to drain, afirst pump having its inlet side communicating with said sump andoperable to remove liquid from said sump, a passageway establishingcommunication between the inlet and outlet sides of said pump, a valvearranged to control said passageway, said valve beingurged in an openingdirection by the output pressure of said pump, and a second pump, saidsecond pump having its inlet side communicating with said sump at alevel above said first pump, the output pressure oi said second pumpbeing effective to urge said valve toward its closed position.

wan-ma n REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 1,477,850 Pool Dec. lo, mas2,305,971 Livingston et al. Dec. 22, 1942

